Process for the recovery of essential oils



Patented May 16, 1939 UNETED STATES PATENT OFFICE PROCESS FOR '1 ESSENTIRECOVERY 0F OILS No Drawing.

5 Claims.

This invention relates to a process for the recovery of essential oils,such as orange oil, lemon oil, lime oil or other oils from citrus fruit.

It is common practice at present to recover.-

orange oil from orange peel by cold pressing the orange rind and pulp toseparatea portion of the oil contained therein and recover the remainderof the oil present in the pressed residue by steam distillation. Theoilrecovered from the pulp by steam distillation is considered inferior tothe cold pressed oil because of the inclusion of undesirableconstituents due to their volatility with the steam. Consequently, theoil which is recovered by steam distillation is of inferior quality tothe cold pressed oil and, therefore has a somewhat lower commercialvalue. The yield of cold pressed oil from orange peel, however, israther low, in fact on the basis of the whole fruit, from 0.1 to 0.3% isabout the highest yield of oil which can be recovered by cold pressing.Therefore, the remainder of the oil which may amount to 0.45 to 0.7% isrecov:

ered by steam distilling the cold pressed rind or Pu pa By our processwe have discovered a method by which we are able to recover a majorportion of the oil present in the citrus'pulp orpeel and at the sametime retain in the recovered oil the degoing'proce'ss 'weare'able torecover as high as sirable quality characteristics of cold pressed oil,

The oil recovered by our process is completely "I soluble in 95% ethylalcohol, which permits its incorporation in alcoholic flavoring extractswithout the necessity of filtration for the preparation of clearsolutions. While it ispossible to treat unpulped orange peel by ourprocess it is preferable that the citrus peel be pulped or ground by anysuitable method into a line slurry 'Ihis'slurry or ground citrus peel isthen extracted with a. suitable solvent which has a high solvent power"for the oil and a minimum solvent power for the undesirable constituentsof the peel'or'puln; "The I solvent solution of the citrus oil is thenseparated from the pulp or slurry and subjectedto distilla-jj I in thepresence or absence of water.

tion for the removal of solvent'from the oil.

More specifically, the process consists in pulp-I- ing the citrus peelorgrinding in the presence of water to form a slurry containing thehighest possiblecontent of essential oil, which upon con ce'ntrationby'rejecting the juice and oil free portions of the fruit may actuallyreach 1 to 5% of essential oil. This pulp or slurry isthen con-Application February 20, 1937, Serial No. 126,886

the essential oil at temperatures substantially above 32 F. inorder toavoid freezing of oil cells which would reduce the yield of oil. Thesolvent and citrus pulp or slurry is then thoroughly agitated for aperiod of time sufliciently long to completely extract the essentialoil. The mixture is then permitted to settle, the heavier pulp prescipitating to the bottom of the container. After removal of a majorportion of the water and pulp by any suitable means, the butane or otherhydrocarbon solution is then separated from the remainder of theinsoluble material by ordinary decantation or by filtration or by acombination of decantation and filtration, or, if desired, the butanesolution may also be separated from the butane insoluble materials bycentrifuging the mass. The butane phase recovered by the foregoingextraction contains the major portion of the essential oil in solutionas well as some undesirable resins. sirable resins from the butanesolution of essential oil, this solution is cooled sufl'lciently tocause the resins present to precipitate. The chilled butane solution isfiltered, centrifuged or settled forthe separation of the precipitatedresinous removal of the butane from the oil. By the foreapproximately90% of the essential-oil present inthe citrus fruit; r

It is, thereforaan' object of the present inven- 'tion to recover citrusoil from citrus fruit or products by means 'of a solvent and to purifythe recovered oil by separating' 'wax'or resinous constituentstherefrom.I I

It is a further object of the present invention to remove wax orresinous material from citrus ,oilby dissolving'thecitrus'oil in anappropriate solvent such as liquid butane, cooling the-solventsolutio'n'of oil to a temperature sufiicie'ntly lowto precipitate thew'axlor resinous material, removing the precipitated resinous or waxymaterial by centrifuging, settling or filtering and then recovering thedewaxed or deresinated oil from the'solution by removing thesolventpresent by distillation. 1 r a It is a further object of thepresentinvention to recover citrusfoil from citrus fruit by preparing apulp or slurry of citrus fruit andcontacting the pulp rating the normalbutane solution or citrus oil from the pulp, chilling the'solution toprecipitate the resinous material present in the solution,

v with an appropriate solvent," such as liquid normal butane, todissolve the on, sepaseparating the precipitated resinous material Ifrom the butane solution of oil and by recovering the oil from thesolution by removing the butane from the distillation.

The following is a specific example of the' method for carrying out ourinvention:

Orange pulp and rind is ground or macerated in the presence of water toform a slurry containing approximately 2 orange oil. This slurry is thenmixed with liquid normal butane at a temperature of about 70 to F. inthe propor tion of 2.75 parts by volume of liquid normal butane to onepart by volume of the orange slurry. The mixture of orange slurry andnormal butane is then agitated at a temperature of 70 to 80 F. for aperiod of about thirty minutes, after which the mass is permitted tosettle for a period up to about twelve hours. A large portion of thewater and solid pulp is then withdrawn from the extraction vessel. Thebutane solution of the orange oil remaining in the extraction vessel isthen cooled to a temperature of about 32 F. for the precipitation of theresinous materials in the solution. The chilled solution is thenfiltered through paper or other suitable medium and thereby freed fromthe precipitated resinous ma- -terial, after which it is heated to aboutF.

for the removal of the major portion of the normal butane and finally toa maximum of 212 F. for not over fifteen minutes to remove any heavyends of the hydrocarbon extractant from the orange oil. The oilrecovered by the foregoing method is equal in quality to cold pressedorange oil and a yield of 86% of the total orange oil present in theslurry is obtained.

The chilling step for the separation of the resinous material is subjectto some variation since certain of the oils extracted contain more ofthe resinous-or waxy material than others. In general a temperature ofabout 32 F. is satisfactory to remove sufficient of these resinousmaterials, however, .we do not wish to limit ourselves to this specifictemperature since we have satisfactorily employed temperatures as low as0 F. for precipitation of the resinous or waxy material from the solventsolution of oil. In carrying out the resin separating step it isimportant to note that it is desirable to leave from 2 to 5% of theresin or wax in the oil since oil containing lower. concentrations thanthese tend to resemble artificial oil and has a somewhat poorer flavor.

We have described liquid normal butane as being the preferred solventsince it has a high solvent power for the essential oils and aminimumsolvent power for the undesirable constituents, its vapor pressure issufflciently low at 70 to 80 F. that it does not necessitate the use ofespeciallyheavy equipment, it is available commercially in asufficiently high state of purity to prevent contamination of theessential oil, and the boiling point is sufficiently low to permitcomplete removal from the essential oil without heating to temperatureshigh enough to impair the quality of the oil. However, we do not wish tolimit ourselves to this solvent since many other solvents may beemployed, as for example, isobutane, liquid ethane, liquid propane, theliquid pentanes, a suitable fraction from casinghead or primary gasolineand mixtures thereof. Furthermore, we may also employ other-solvents, asfor example, ketones such as acetone and methyl acetone, and ethers suchas ethyl and isopropyl ether or mixtures of those solvents. Preferablythe solvents which we employ should have a lower boiling point than thatof the citrus oil in order to permit good fractional distillationbetween the oil and solvent. Furthermore the solvents should be freefrom malodorous or maltasting constituents which impart to the oil a badtaste or odor. It is also preferable that the solvent employed shouldnot be water soluble to any appreciable extent. In some instances thesolvent may be treated for removal of constituents present whichunfavorably influence the quality of the oil. For example, low boilinghydrocarbon solvents may be pretreated with caustlcsoda for the removalof hydrogen sulphide or mercaptans both of which impart a highlyundesirable odor to citrus oil. Furthermore, we have described a processin which 2.75 volumes of solvent and one volume of citrus are mixedtogether for the recovery of the oil, but we do not wish to limitourselves to these proportions since in many cases it may be desirableto alter this ratio. In some instances it may require three or fourvolumes of the liquid butane to one volume of the citrus pulp or slurryand in other instances it may be desirable to use equal or even smallervolumes of solvent than of pulp ,or slurry.

We have described a process in which we have employed an extractiontemperature of about that of atmospheric, namely 70 F. to 80 F. However,we do not wish to limit ourselves to this temperature since in someinstances it may be desirable to employ temperatures which are greatlyin excess of atmospheric, for example, the orange slurry may be chargedinto a pressure bomb together with the liquid normal butane and thismixture may be heated to a temperature of about F. to 200 F. togetherwith agitation in order to insure complete solution of the oil in thesolvent. After complete solution, the mixture, may then be cooled andafter removal of the water and 'the resinous materials present in thesolution by cooling and separating, as described above, the orange oilmay then be recovered by simply removing the normal butane present.

Another modification of the process consists in leaching the slurry at atemperature at which the resinous material will not go into solution.This temperature will be about 32 F. to 35 F. At this temperature theslurry is a solid mass due to the crystallization of the water present.When operating according to this cold leaching method the chilled slurryat a temperature of 32 F. to 35 F. is intimately mixed with chillednormal butane at about the same temperature.

After thorough agitation the chilled mixture con-- taining the dissolvedorange oil is then separated.

from the insoluble pulp and after filtration to remove any solidmaterial which may be present the solvent is removed from the oil bydistillation.

It is to be understood that these disclosures are presented asillustrative of the generic invention solvent under sufl'icient pressureto maintain said solvent in a liquid state, settling the mixture ofslurry and solvent under pressure and thereby forming a solvent layercontainingthe citrus oil and a slurry layer, separating said layers,cooling the solvent layer to precipitate resinous material, removing theprecipitated resinous material from the solvent layer and removing thesolvent from the de-resinated oil. i

2. A process according to claim 1 in which the solvent is liquid butane.

3. A process according to claim 1 in which the solvent layer is cooledto a temperature between 0 F. and 32 F. for precipitation of theresinous material.

4. A process for the purification of citrus oil containing resinousimpurities which comprises grinding citrus peel with water and therebyforming a slurry, commingling said slurry with cooled liquefied normallygaseous hydrocarbon solvent under suflicient pressure to maintain saidsolvent in a liquid state, settling the mixture under pressure andthereby forming a liquidsolvent layer containing the citrus oil and aslurry layer, separating said layers, and removing the solvent from thelayer containing the citrus oil.

5. A process according to claim 4 in which the leaching temperature isbetween 0 F. and 32 F.

CHARLES DOUGLAS BARNES. WILLIAM A. S. WRIGHT.

